1. Field of the Invention
This invention relates to molded case circuit breakers and more particularly to a mechanical interlock which trips the circuit breaker any time it is lifted away from its panel mounting.
2. Description of the Prior Art
Molded case circuit breakers are generally old and well-known in the art. Examples of such circuit breakers are disclosed in U.S. Pat. Nos. 4,489,295; 4,638,277; 4,656,444 and 4,679,018. Such circuit breakers are generally used to protect electrical circuitry from damage due to an overcurrent condition, such as an overload and a relatively high level short circuit condition. An overload condition is normally 200 to 300 percent of the nominal current rating of the circuit breaker. A high level short circuit condition can be 1000 percent or more of the nominal current rating of the circuit breaker.
Molded case circuit breakers generally include at least one pair of separable main contacts which may be operated manually by way of an operating handle, extending outwardly from the circuit breaker case or automatically in response to an overcurrent or high level short circuit condition. In the manual mode and one automatic mode of operation, the separable main contacts are opened by an operating mechanism which, in turn, is actuated by either a trip unit in the automatic mode or the operating handle in the manual mode. In another automatic mode of operation, magnetic repulsion forces, generated between the stationary and movable contacts during relatively high level overcurrent conditions, can also cause the main contacts to be separated independently of the operating mechanism.
Molded case circuit breakers are generally provided with one or more line side terminals and one or more load side terminals. Oftentimes the line and load side terminals are provided with rear terminations to allow them to be plugged into corresponding receptacles on a circuit breaker panel. The line side receptacles on the circuit breaker panel are generally connected to a common source of electrical power. The load side receptacles on the circuit breaker panel are connected to various electrical loads.
Sometimes it is necessary to remove a circuit breaker from its panel mounting after it has been placed in service. For example, the circuit breaker may need to be removed for servicing or maintenance. Additionally, the circuit breaker may have to be removed and replaced with another circuit breaker with a different current rating due to a change in the load requirements.
Circuit breakers with plug in type rear terminations may be removed from the circuit breaker panel by unfastening the circuit breaker and pulling it outwardly from the panel. Such action will disconnect the circuit breaker load side and line side terminations from the corresponding receptacles on the circuit breaker panel. If the circuit breaker is on and is supplying electrical power to a load, electrical current will be flowing through the circuit breaker line side and load side terminations and corresponding receptacles on the circuit breaker panel. Should the circuit breaker be removed from its panel mounting while electrical current is flowing therethrough the electrical circuit would be broken between the terminations on the circuit breaker and the corresponding receptacles on the panel causing an arc to be drawn therebetween.
In many known circuit breakers, there are no means for automatically tripping the circuit breaker prior to its being removed from the panel. With such circuit breakers it is incumbent on the operator to manually trip the circuit breaker before removing it from the panel.